Disturbances in gamma-amino butyric acid (GABA) function recently have been hypothesized to contribute to the neurobiology of Major Depression. Electroconvulsive Therapy (ECT), a highly effective form of treatment for this disorder is likely to alter GABA function. This study will investigate the effects of ECT on GABA levels and clinical response. This information may provide new insight into the underlying pathophysiology of Major Depression and the mechanism of action of ECT.